This invention relates to a spindle device of a machine tool spouting spray coolant from the tip of a tool.
As to machining by machine tools, much coolant is supplied into machining points to cool and lubricate workpieces and tools, or to eliminate cutting chips. In this case, there are many problems, such as ill effects to an environmental pollution and human health due to coolant, high cost resulting from waste oil disposal of the coolant, shortening the life of a tool resulting from undercooling the workpieces, and sliding friction due to excessive coolant at a minute slitting of the tool. Besides, much coolant adheres to the cutting chips in machining, and therefore, when treating and recycling cutting chips, the adhesive coolant must be separated.
In recent years, to settle the above problems, there appear machine tools performing so-called dry cutting that cut as supplying spray into machining points. Here, the spray is formed from a very small quantity of coolant.
Applicant has already practiced machine tools for the dry cutting, for example, their spindle device is like FIG. 5 or FIG. 6.
First, an explanation about FIG. 5 will follow. Numeral 2 is a spindle, 7 is a draw-bar, and 11 is a clamp-rod. Here, the draw-bar 7 is provided in the center of the spindle 2, and the clamp-rod 11 is screwed on the tip of the draw-bar 7. Besides, an in-spindle spray coolant passage 102 is provided over both centers of the draw-bar 7 and the clamp-rod 11. Numeral 18c is a tapered interfitting axis of a tool holder 18, which is closely fitted into a tapered interfitted hole 5a provided in the tip of the spindle 2, pulled backward f2 by a collet 12, and comes to be in grasp. Numeral 14 is an atomizing nozzle for coolant, 103 is an in-holder spray coolant passage provided in the center of the tool holder 18. The front end of the passage 103 opens to the tip face of the tool fixed on the tool holder 18, and the rear end thereof opens to a bottom face of a cavity xe2x80x9cbxe2x80x9d provided in the center of the tapered interfitting axis 18c. 
Next, an explanation about FIG. 6 will follow. A canister 25 is fixed at the center of the spindle 2, and a steel ball 26 is supported on a through hole 25a on a peripheral wall of the canister 25 so as to be displaced in radial direction. The steel ball 26 is pushed to a wedge-shaped cavity 27 in accordance with the backward displacement of the clamp-rod 11 combined with the draw-bar 7, displaced in outward radial direction of the canister 25, and fitted into a circular hole b1 provided on a peripheral wall of the tapered interfitting axis 18c of the tool holder 18, thereby pulling the tapered intermitting axis 18c backward f2. Hence, the tapered interfitting axis 18c comes to be in grasp. The others are same with those of FIG. 5.
In FIG. 5 or FIG. 6, spray coolant spouts from an outlet of the atomizing nozzle 14 within the spindle 2 into the in-spindle spray coolant passage 102. The spouted spray coolant flows into the cavity xe2x80x9cbxe2x80x9d of the tool holder 18 from the front opening of the clamp-rod 11, and then flows out the air from the tip of the tool through the in-holder spray coolant passage 103 and a spray coolant passage provided in the center of the tool fixed on the holder 18.
According to this kind of machine tool, even if the tool cuts deep position of a workpiece, its machining point is effectively lubricated by the spray coolant spouted from the tip of the tool. Accordingly, cutting is rationally accomplished.
However, according to the above conventional machine tool, the spray coolant reached the inside of the cavity xe2x80x9cbxe2x80x9d of the tool holder 18 flows out the air through an opening between parts. Therefore the coolant is wasted.
Besides, since the cavity xe2x80x9cbxe2x80x9d has a comparative large diameter in comparison with its front and back passages, the spray coolant reached the cavity xe2x80x9cbxe2x80x9d is liquefied. The liquefaction hinders the coolant from being stably supplied to the machining point of the workpiece, and does harm to a response to start or stop spouting the spray coolant from the tip of the tool.
Objects of the present invention are to provide a spindle device of a machine tool which can settle the above problems.
To achieve the above objects, in a spindle device of the present invention, as shown in claim 1, a machine tool fixs mechanical-detachably a tool holder on the tip of a spindle by collet-clamping means. A mouthpiece member in a fixed length is protrudently installed on the bottom face of a cavity formed in the center of the tool holder with a screw. A gas-liquid passage, an atomizing means and an in-spindle spray coolant passage are provided in the center of a draw-bar of a spindle side clamping means. The atomizing means comprises an atomizing nozzle and a compressed air supplying valve. The atomizing nozzle mixes and stirs coolant and compressed air which are supplied from the outside of the spindle through the gas-liquid passage, and generates spray coolant. When pressure of the spray coolant spouted into the in-spindle spray coolant passage in front of the nozzle falls, the compressed air supplying valve is displaced forward a little, and directly blows the compressed air within a compressed air passage into the spray coolant. The in-spindle spray coolant passage is formed from an inner hole of the compressed air supplying valve, and contacts on the rear end of the mouthpiece member of the above tool holder.
Accordingly, the in-spindle spray coolant passage, the in-holder spray coolant passage, and the extension passage are hardly different in their diameters, and are closely communicated with each other. Therefore, the spray coolant passing these passages is prevented being liquefied by vast differences between their diameters, and stably spouting from the tip of a tool of the tool holder. Besides, since these passages are closely connected, the spray coolant is prevented flowing out the air in vain through an opening between parts. Moreover, since the extension passage is provided to the tool holder, a structure of the conventional spindle side can be used as it is.
This invention can be materialized as follows.
That is, as shown in claim 2, an external form of the compressed air supplying valve is formed in one having level difference of a large diameter portion and a small diameter portion. The small diameter portion is located in an central hole of a joint screw fitted in an inner hole of a clamp-rod of the clamping means. A spring is provided between the joint screw and the level difference, and presses the compressed air supplying valve to the atomizing nozzle side.
In this case, as shown in claim 3, when fastening the tool holder, the tip of the small diameter portion of the compressed air supplying valve is partially inserted into the rear end of the mouthpiece member of the tool holder.
Moreover, in the tool holder of the present invention, the extension passage is provided in the center of the bottom face of a comparative large diameter cavity provided on a tapered intermitting axis in the state that the in-holder spray coolant passage provided in the center of a holder body is extended backward. Accordingly, conventional clamping means can be almost used as it is.
In this case, the extension passage may be provided so as to go in and out in its longitudinal direction, as well as so as to be pressed backward by spring force.